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Unlabelled: Natural killer (NK) cells play an important role in tumor immunotherapy with their unique capability of killing transformed cells without the need for prior sensitization and without major histocompatibility complex (MHC)/peptide restriction. However, tumor cells can escape NK cell cytotoxicity by various tumor immune escape mechanisms. To overcome these escape mechanisms, NK cells can be modified to express chimeric antigen receptors (CARs), enhancing their tumor-specific cytotoxicity. To determine the most efficacious method to modify human NK cells, we compared different retroviral vector systems, retroviral pseudotypes, and transduction protocols. Using optimized transduction conditions, the highest transduction levels (up to 60%) were achieved with alpharetroviral vectors. Alpharetroviral-modified primary human NK cells exhibited no alteration in receptor expression and had similar degranulation activity as untransduced NK cells, thus demonstrating that alpharetroviral modification did not negatively affect NK cell cytotoxicity. Transduction of NK cells with an alpharetroviral vector containing a CD19 CAR expression cassette selectively enhanced NK cell cytotoxicity towards CD19-expressing leukemia cells, achieving nearly complete elimination of leukemia cells after 48 h. Taken together, alpharetroviral vectors are promising tools for NK cell-mediated cancer immunotherapy applications., Key Messages: Efficient modification of human NK cells using alpharetroviral vectors. Anti-CD19-CAR-NK cells exhibited improved cytotoxicity towards CD19(+) leukemia cells. Alpharetroviral vectors are promising tools for immunotherapy applications using NK cells.

Background: Reactivation of latent viruses such as human cytomegalovirus (HCMV) after allogeneic hematopoietic stem cell transplantation (HSCT) results in high morbidity and mortality. Effective immunization against HCMV shortly after allo-HSCT is an unmet clinical need due to delayed adaptive T cell development. Donor-derived dendritic cells (DCs) have a critical participation in stimulation of naïve T cells and immune reconstitution, and therefore adoptive DC therapy could be used to protect patients after HSCT. However, previous methods for ex vivo generation of adoptive donor-derived DCs were complex and inconsistent, particularly regarding cell viability and potency after thawing. We have previously demonstrated in humanized mouse models of HSCT the proof-of-concept of a novel modality of lentivirus-induced DCs ("SmyleDCpp65") that accelerated antigen-specific T cell development., Methods: Here we demonstrate the feasibility of good manufacturing practices (GMP) for production of donor-derived DCs consisting of monocytes from peripheral blood transduced with an integrase-defective lentiviral vector (IDLV, co-expressing GM-CSF, IFN-α and the cytomegalovirus antigen pp65) that were cryopreserved and thawed., Results: Upscaling and standardized production of one lot of IDLV and three lots of SmyleDCpp65 under GMP-compliant conditions were feasible. Analytical parameters for quality control of SmyleDCpp65 identity after thawing and potency after culture were defined. Cell recovery, uniformity, efficacy of gene transfer, purity and viability were high and consistent. SmyleDCpp65 showed only residual and polyclonal IDLV integration, unbiased to proto-oncogenic hot-spots. Stimulation of autologous T cells by GMP-grade SmyleDCpp65 was validated., Conclusion: These results underscore further developments of this individualized donor-derived cell vaccine to accelerate immune reconstitution against HCMV after HSCT in clinical trials.

Background: The complex cellular networks within tumors, the cytokine milieu, and tumor immune escape mechanisms affecting infiltration and anti-tumor activity of immune cells are of great interest to understand tumor formation and to decipher novel access points for cancer therapy. However, cellular in vitro assays, which rely on monolayer cultures of mammalian cell lines, neglect the three-dimensional architecture of a tumor, thus limiting their validity for the in vivo situation., Methods: Three-dimensional in vivo-like tumor spheroid were established from human cervical carcinoma cell lines as proof of concept to investigate infiltration and cytotoxicity of NK cells in a 96-well plate format, which is applicable for high-throughput screening. Tumor spheroids were monitored for NK cell infiltration and cytotoxicity by flow cytometry. Infiltrated NK cells, could be recovered by magnetic cell separation., Results: The tumor spheroids were stable over several days with minor alterations in phenotypic appearance. The tumor spheroids expressed high levels of cellular ligands for the natural killer (NK) group 2D receptor (NKG2D), mediating spheroid destruction by primary human NK cells. Interestingly, destruction of a three-dimensional tumor spheroid took much longer when compared to the parental monolayer cultures. Moreover, destruction of tumor spheroids was accompanied by infiltration of a fraction of NK cells, which could be recovered at high purity., Conclusion: Tumor spheroids represent a versatile in vivo-like model system to study cytotoxicity and infiltration of immune cells in high-throughput screening. This system might proof useful for the investigation of the modulatory potential of soluble factors and cells of the tumor microenvironment on immune cell activity as well as profiling of patient-/donor-derived immune cells to personalize cellular immunotherapy.

5-Lipoxygenase (5-LO) is the key enzyme in leukotriene biosynthesis. Leukotrienes are mediators of the innate immune system and inflammatory processes, and they might also be involved in cancer development. MicroRNAs (miRNAs) are important translational regulators and have been shown to be involved in development, differentiation, and cancer. Unraveling the miRNA network is important for understanding the cellular regulation processes. We identified two new miRNAs, miR-19a-3p and miR-125b-5p, regulating 5-LO and confirmed direct interaction by reporter gene assays. Furthermore, we investigated the regulation of 5-LO by these two miRNAs in several cell types. Inhibition of both miRNAs by antagomirs during differentiation of the myeloid cell line Mono Mac 6 led to a significant increase in 5-LO protein expression. Stimulation of human T lymphocytes with PHA resulted in a strong downregulation of 5-LO mRNA expression and in the induction of miR-19a-3p. The inhibition of miR-19a-3p with an antagomir led to a significant increase in 5-LO mRNA expression in T lymphocytes. Taken together, our data reveal that miR-19a-3p and miR-125b-5p target 5-LO in a cell type- and stimulus-specific manner., (Copyright © 2015 by The American Association of Immunologists, Inc.)

In contrast to donor T cells, natural killer (NK) cells are known to mediate anti-cancer effects without the risk of inducing graft-versus-host disease (GvHD). In order to improve cytotoxicity against resistant cancer cells, auspicious efforts have been made with chimeric antigen receptor (CAR) expressing T- and NK cells. These CAR-modified cells express antigen receptors against tumor-associated surface antigens, thus redirecting the effector cells and enhancing tumor-specific immunosurveillance. However, many cancer antigens are also expressed on healthy tissues, potentially leading to off tumor/on target toxicity by CAR-engineered cells. In order to control such potentially severe side effects, the insertion of suicide genes into CAR-modified effectors can provide a means for efficient depletion of these cells. While CAR-expressing T cells have entered successfully clinical trials, experience with CAR-engineered NK cells is mainly restricted to pre-clinical investigations and predominantly to NK cell lines. In this review we summarize the data on CAR expressing NK cells focusing on the possible advantage using these short-lived effector cells and discuss the necessity of suicide switches. Furthermore, we address the compliance of such modified NK cells with regulatory requirements as a new field in cellular immunotherapy.

We report on a series of sequential events leading to long-term survival and cure of pediatric X-linked chronic granulomatous disease (X-CGD) patients after gamma-retroviral gene therapy (GT) and rescue HSCT. Due to therapyrefractory life-threatening infections requiring hematopoietic stem cell transplantation (HSCT) but absence of HLAidentical donors, we treated 2 boys with X-CGD by GT. Following GT both children completely resolved invasive Aspergillus nidulans infections. However, one child developed dual insertional activation of ecotropic viral integration site 1 (EVI1) and signal transducer and activator of transcription 3 (STAT3) genes, leading to myelodysplastic syndrome (MDS) with monosomy 7. Despite resistance to mismatched allo-HSCT with standard myeloablative conditioning, secondary intensified rescue allo-HSCT resulted in 100 % donor chimerism and disappearance of MDS. The other child did not develop MDS despite expansion of a clone with a single insertion in the myelodysplasia syndrome 1 (MDS1) gene and was cured by early standard allo-HSCT. The slowly developing dominance of clones harboring integrations in MDS1-EVI1 may guide clinical intervention strategies, i.e. early rescue allo-HSCT, prior to malignant transformation. GT was essential for both children to survive and to clear therapy-refractory infections, and future GT with safer lentiviral self-inactivated (SIN) vectors may offer a therapeutic alternative for X-CGD patients suffering from life-threatening infections and lacking HLA-identical HSC donors.

Background: The adoptive transfer of allogeneic antiviral T lymphocytes derived from seropositive donors can safely and effectively reduce or prevent the clinical manifestation of viral infections or reactivations in immunocompromised recipients after hematopoietic stem cell (HSCT) or solid organ transplantation (SOT). Allogeneic third party T-cell donors offer an alternative option for patients receiving an allogeneic cord blood transplant or a transplant from a virus-seronegative donor and since donor blood is generally not available for solid organ recipients. Therefore we established a registry of potential third-party T-cell donors (allogeneic cell registry, alloCELL) providing detailed data on the assessment of a specific individual memory T-cell repertoire in response to antigens of cytomegalovirus (CMV), Epstein-Barr virus (EBV), adenovirus (ADV), and human herpesvirus (HHV) 6., Methods: To obtain a manufacturing license according to the German Medicinal Products Act, the enrichment of clinical-grade CMV-specific T cells from three healthy CMV-seropositive donors was performed aseptically under GMP conditions using the CliniMACS cytokine capture system (CCS) after restimulation with an overlapping peptide pool of the immunodominant CMVpp65 antigen. Potential T-cell donors were selected from alloCELL and defined as eligible for clinical-grade antiviral T-cell generation if the peripheral fraction of IFN-γ(+) T cells exceeded 0.03% of CD3(+) lymphocytes as determined by IFN-γ cytokine secretion assay., Results: Starting with low concentration of IFN-γ(+) T cells (0.07-1.11%) we achieved 81.2%, 19.2%, and 63.1% IFN-γ(+)CD3(+) T cells (1.42 × 10(6), 0.05 × 10(6), and 1.15 × 10(6)) after enrichment. Using the CMVpp65 peptide pool for restimulation resulted in the activation of more CMV-specific CD8(+) than CD4(+) memory T cells, both of which were effectively enriched to a total of 81.0% CD8(+)IFN-γ(+) and 38.4% CD4(+)IFN-γ(+) T cells. In addition to T cells and NKT cells, all preparations contained acceptably low percentages of contaminating B cells, granulocytes, monocytes, and NK cells. The enriched T-cell products were stable over 72 h with respect to viability and ratio of T lymphocytes., Conclusions: The generation of antiviral CD4(+) and CD8(+) T cells by CliniMACS CCS can be extended to a broad spectrum of common pathogen-derived peptide pools in single or multiple applications to facilitate and enhance the efficacy of adoptive T-cell immunotherapy.

In a clinical phase I/II trial, pediatric patients with high-risk malignancies were treated with ex vivo IL-2-stimulated donor natural killer (NK) cells after transplantation with haploidentical stem cells. To evaluate the potential negative effects of the immunosuppressive drug mycophenolate mofetil (MMF) used for immunotherapy, the functionality and signaling of ex vivo NK cells was investigated. Our results show that during NK cell expansion, long-term (9 days) incubation with mycophenolic acid (MPA), the active metabolite of MMF, in therapeutically relevant concentrations led to the severe inhibition of NK cell proliferation. This correlated with a significantly reduced cytokine/chemokine secretion and the inhibited acquisition of surface receptors regarding cytotoxicity (e.g., NKp30, NKp44, NKp46, NKG2D), adhesion/migration (e.g., ICAM-1/CD54, LFA-1/CD11a, CD62L, CXCR3) and activation (e.g., CD25). Moreover, MPA prevented phosphorylation of the central signaling molecules STAT-3/-4/-5, AKT and ERK1/2. In contrast, short-term (24 h) MPA incubation of IL-2-stimulated NK cells had no or only marginal effects on the activated NK cell phenotype, including receptor expression, cytokine/chemokine secretion and intracellular signaling. Further, short-term MPA incubation only moderately affected the highly cytotoxic activity of previously IL-2-stimulated NK cells. In conclusion, while long-term MPA incubation significantly compromised ex vivo NK cell functionality, previously IL-2-activated NK cells seemed to be rather resistant to short-term MPA treatment. This finding supports the use of IL-2-activated NK cells as immunotherapy, especially for patients treated with MMF after haploidentical stem cell transplantation.

Multimer monitoring has become a standard technique for detection of antigen-specific T cells. The term "multimer" refers to a group of reagents based on the multimerisation of molecules in order to raise avidity and thus stabilize binding to their ligand. Multimers for detection of antigen-specific T-cell responses are based on major histocompatibility complex class I peptide complexes. Multimer staining enables fast and direct visualization of antigen-specific T cells; thus, it is widely applied to assess antiviral immunity, e.g., monitor patients in vaccination trials or confirm purity of cell products for adoptive transfer. Assessment of T-cell immunity against persistent pathogens like cytomegalovirus (CMV) is of major importance in immunosuppressed patients. Recent advancements of multimers facilitate reversible labeling and allow isolation of epitope-specific T cells for adoptive transfer. Here, we give an overview on the different multimers and their applications, with an emphasis on CMV-specific T-cell responses., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Background Aims: Advanced therapy medicinal products (ATMP) are gene therapy, somatic cell therapy or tissue-engineered products regulated under (EC) No. 1394/2007 to ensure their free movement within the European Union while guaranteeing the highest level of health protection for patients. Academic good manufacturing practice (GMP) centers are major contributors in the development of ATMPs and this study assessed the impact of regulations on them., Methods: European academic and non-industrial facilities (n = 747) were contacted, and a representative sample of 50 replied to a detailed questionnaire. Experienced centres were further selected in every Member State (MS) for semi-structured interviews. Indicators of ATMP production and development success were statistically assessed, and opinions about directive implementation were documented., Results: Facilities experienced in manufacturing cell therapy transplant products are the most successful in developing ATMPs. New centres lacking this background struggle to enter the field, and there remains a shortage of facilities in academia participating in translational research. This is compounded by heterogeneous implementation of the regulations across MS., Conclusions: GMP facilities successfully developing ATMPs are present in all MS. However, the implementation of regulations is heterogeneous between MS, with substantial differences in the definition of ATMPs and in the approved manufacturing environment. The cost of GMP compliance is underestimated by research funding bodies. This is detrimental to development of new ATMPs and commercialization of any that are successful in early clinical trials. Academic GMP practitioners should strengthen their political visibility and contribute to the development of functional and effective European Union legislation in this field., (Copyright © 2014 International Society for Cellular Therapy. All rights reserved.)

The insight that the immune system is able to eradicate tumor cells inspired the development of targeted immunotherapies. These novel approaches aim to trigger immune molecules and receptors, including CD3 on T cells and NKG2D and NKp30 on natural killer (NK) cells, to harness the immune system against cancer. In cancer patients, overcoming immune suppression induced by malignant cells or by the tumor microenvironment remains the major challenge to the clinical efficacy of immunotherapies. Recombinant constructs have been developed in various formats either utilizing natural ligands (immunoligands) or antibody-derived components (immunoconstructs) to circumvent mechanisms that counteract an effective antitumor immune response., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Background Aims: Natural killer (NK) cells, either naive or genetically engineered, are increasingly considered for cellular therapy of patients with malignancies. When using NK cells from peripheral blood, the number of expanded NK cells can be highly variable and the need for NK cell enrichment can make the process expensive. The NK-92 cell line (CD56+/CD3-) that was isolated from a patient with lymphoma has predictable high cytotoxic activity and can be expanded under good manufacturing practice conditions in recombinant interleukin-2., Methods: Fifteen patients (age, 9-71 years) with advanced, treatment-resistant malignancies, either solid tumors/sarcomas (n = 13) or leukemia/lymphoma (n = 2), received two infusions of NK-92 cells, given 48 h apart. Three cohorts of patients were treated with escalating doses of NK-92 cells (n = 7 at 1 × 10(9), n = 6 at 3 × 10(9) and n = 2 at 1 × 10(10) cells/m(2))., Results: No infusion-related or long-term side effects were observed. The dose of 10(10) cells/m(2) was considered the maximum expandable cell dose with the use of an established culture bag system. Three fourths of patients with lung cancer had some anti-tumor response. Only one patient of seven had development of human leukocyte antigen antibodies. The persistence of NK-92 cells (male origin) in the circulation was confirmed by Y chromosome-specific polymerase chain reaction in two female patients., Conclusions: Infusions of NK-92 cells up to 10(10) cells/m(2) were well tolerated. Despite the allogeneic nature of NK-92, development of human leukocyte antigen antibodies in these patients with cancer appears to be rare. The cells can persist in the recipient's circulation for at least 48 h. Some encouraging responses were seen in patients with advanced lung cancer., (Copyright © 2013 International Society for Cellular Therapy. Published by Elsevier Inc. All rights reserved.)

Mucormycosis has a high mortality and is increasingly diagnosed in hematopoietic stem cell transplant (HSCT) recipients. In this setting, there is a growing interest to restore host defense to combat infections by adoptively transferring donor-derived immunocompetent cells. Natural killer (NK) cells exhibit antitumor and antiinfective activity, but the interaction with Mucormycetes is unknown. Our data demonstrate that both unstimulated and IL-2 prestimulated human NK cells damage Rhizopus oryzae hyphae, but do not affect resting conidia. The damage of the fungus is mediated, at least in part, by perforin. R. oryzae hyphae decrease the secretion of immunoregulatory molecules by NK cells, such as IFN-γ and RANTES, indicating an immunosuppressive effect of the fungus. Our data indicate that NK cells exhibit activity against Mucormycetes and future research should evaluate NK cells as a potential tool for adoptive immunotherapy in HSCT., (Copyright © 2012 Elsevier GmbH. All rights reserved.)

Allogeneic natural killer (NK) cells are used for adoptive immunotherapy after stem cell transplantation. In order to overcome technical limitations in NK cell purification and activation, the following study investigates the impact of different variables on NK cell recovery, cytotoxicity, and T-cell depletion during good manufacturing practice (GMP)-grade NK cell selection. Forty NK cell products were derived from 54 unstimulated donor leukaphereses using immunomagnetic CD3 T-cell depletion, followed by a CD56 cell enrichment step. For T-cell depletion, either the depletion 2.1 program in single or double procedure (D2.11depl, n = 18; D2.12depl, n = 13) or the faster depletion 3.1 (D3.1, n = 9) was used on the CliniMACS instrument. Seventeen purified NK cell products were activated in vitro by IL-2 for 12 days. The whole process resulted in a median number of 7.59 × 10(8) CD56(+)CD3(-) cells with both purity and viability of 94%, respectively. The T-cell depletion was significantly better using D2.11depl/2depl compared to D3.1 (log 4.6/log 4.9 vs. log 3.7; p < 0.01) and double procedure in two stages led always to residual T cells below 0.1%. In contrast D3.1 was superior to D2.11depl/2depl with regard to recovery of CD56(+)CD3(-) NK cells (68% vs. 41%/38%). Concomitant monocytes and especially IL-2 activation led to increased NK cell activity against malignant target cells compared to unstimulated NK cells, which correlated with both up-regulation of natural cytotoxicity receptors and intracellular signaling. Overall, wide variations in the NK cell expansion rate and the distribution of NK cell subpopulations were found. In conclusion, our results indicate that GMP-grade purification of NK cells might be improved by a sequential processing of T-cell depletion program D2.1 and D3.1. In addition NK cell expansion protocols need to be further optimized.

Aims: Ageing of the immune system, immunosenescence, is characterized by impaired lymphopoiesis, especially B-lymphocyte maturation, and is a hallmark of chronic heart failure (CHF). MicroRNAs (miRNAs) are non-coding, small RNAs, which post-transcriptionally control gene expression of multiple target genes. The miR-181 family is known to control haematopoietic lineage differentiation. Here, we study the role of the miR-181 family in immunosenescence and CHF., Methods and Results: We conducted a clinical study analysing peripheral blood (PB) for miRNA expression and leucocyte distribution of young healthy controls (25 ± 4 years; n = 30), aged healthy controls (64 ± 5 years; n = 13), and age-matched CHF patients (64 ± 11years; n = 18). The expression of miR-181 family members was reduced, whereas miR-34a was increased in PB of aged individuals. In particular, miR-181c was further reduced in age-matched CHF patients. In PB, we observed reduced numbers of lymphocytes, in particular cytotoxic T cells and B cells, with rising age, and the expression of miR-181 correlated with the number of B cells. Notably, in CHF patients, ischaemic heart failure was associated with a further reduction of total B cells as well as their subpopulations, such as memory B cells, compared with age-matched healthy volunteers., Conclusions: Ageing- and CHF-associated changes in PB leucocyte subsets are paralleled by alterations in the expression of miRNAs involved in lymphopoiesis, which might play an important role in the age-related and CHF-mediated dysregulation of immune functions resulting in immunosenescence. Furthermore, miR-181c may serve as a marker for reduced immune functions in CHF patients.

As a result of improved experimental methodologies and a better understanding of the immune system, there is increasing insight into the antifungal activity of natural killer (NK) cells. Murine and human NK cells are able to damage fungi of different genera and species in vitro, and they exert both direct and indirect antifungal activity through cytotoxic molecules such as perforin and through cytokines and interferons, respectively. On the other hand, recent data suggest that fungi exhibit immunosuppressive effects on NK cells. Whereas clear in vivo data are lacking in humans, the importance of NK cells in the host response against fungi has been demonstrated in animal models. Further knowledge of the interaction of NK cells with fungi might help to better understand the pathogenesis of invasive fungal infections and to improve treatment strategies.

Dendritic cells (DCs) are the most potent antigen-presenting cells and are the key link between the innate and adaptive immune response. Only a few reports with study populations of up to 50 individuals have been published with age-based reference values for DC subpopulations in healthy children. Therefore, we aimed to establish reference ranges in a larger study population of 100 healthy children, which allowed age-matched subgroups. Most previous studies were performed using a dual-platform approach. In this study, a single-platform approach in a lyse no-wash procedure was used. DC subpopulations were defined as follows: CD45(+) CD85k(+) HLA-DR(+) CD14(-) CD16(-) CD33(+) cells as myeloid DCs (mDCs) and CD45(+) CD85k(+) HLA-DR(+) CD14(-) CD16(-) CD123(+) cells as plasmacytoid DCs (pDCs). Reference ranges were established using a semi-parametric regression of age-matched absolute and relative DC counts. We found a significant decline with increasing age in the medians of mDCs (P = 0.0003) and pDCs per μl peripheral blood (PB) (P = 0.004) and in the 50%, 90% and 95% reference ranges. We also identified significantly lower absolute cell counts of mDCs per μl PB in girls than in boys for all age groups (P = 0.0015). Due to the larger paediatric study population and single-platform approach, this study may give a more precise overview of the normal age-matched development of DC subpopulations and may provide a basis for analyzing abnormal DC counts in different illnesses or therapies such as post stem cell transplantation., (© 2013 The Authors. Scandinavian Journal of Immunology © 2013 Blackwell Publishing Ltd.)

Adoptive immunotherapy with allogeneic purified natural killer (NK) cell products might exert graft-versus-tumor alloreactivity with little risk of GVHD. In a prospective phase II study in two centers, we administered purified NK cell products to high-risk patients treated with haploidentical T-cell-depleted SCT. Sixteen patients received a total of 29 NK cell infusions on days +3, +40 and +100 after transplantation. Median doses (and ranges) of infused NK- and T-cells per product were 1.21 (0.3-3.8) × 10(7)/kg and 0.03 (0.004-0.72) × 10(5)/kg, respectively. With a median follow-up of 5.8 years 4/16 patients are alive. Cause of death was relapse in five, GVHD in three, graft failure in three, and transplant related neurotoxicity in one patient. Four patients developed acute GVHDgrade II, all receiving a total of 0.5 × 10(5) T cells/kg. Compared with historical controls, NK cell infusions had no apparent effect on the rates of graft failure or relapse. Adoptive transfer of allogeneic NK cells is safe and feasible, but further studies are needed to determine the optimal dose and timing of NK cell therapy. Moreover, NK cell activation/expansion may be required to attain clinical benefit, while careful consideration must be given to the number of T cells infused.

Treatment of high-risk neuroblastoma (NB) represents a major challenge in paediatric oncology. Alternative therapeutic strategies include antibodies targeting the disialoganglioside GD(2) , which is expressed at high levels on NB cells, and infusion of donor-derived natural killer (NK) cells. To combine specific antibody-mediated recognition of NB cells with the potent cytotoxic activity of NK cells, here we generated clonal derivatives of the clinically applicable human NK cell line NK-92 that stably express a GD(2) -specific chimeric antigen receptor (CAR) comprising an anti-GD(2) ch14.18 single chain Fv antibody fusion protein with CD3-ζ chain as a signalling moiety. CAR expression by gene-modified NK cells facilitated effective recognition and elimination of established GD(2) expressing NB cells, which were resistant to parental NK-92. In the case of intrinsically NK-sensitive NB cell lines, we observed markedly increased cell killing activity of retargeted NK-92 cells. Enhanced cell killing was strictly dependent on specific recognition of the target antigen and could be blocked by GD(2) -specific antibody or anti-idiotypic antibody occupying the CAR's cell recognition domain. Importantly, strongly enhanced cytotoxicity of the GD(2) -specific NK cells was also found against primary NB cells and GD(2) expressing tumour cells of other origins, demonstrating the potential clinical utility of the retargeted effector cells., (© 2012 Foundation for Cellular and Molecular Medicine/Blackwell Publishing Ltd.)

Background: Reconstitution of cytomegalovirus-specific CD3(+)CD8(+) T cells (CMV-CTLs) after allogeneic hematopoietic stem cell transplantation (HSCT) is necessary to bring cytomegalovirus (CMV) reactivation under control. However, the parameters determining protective CMV-CTL reconstitution remain unclear to date., Design and Methods: In a prospective tri-center study, CMV-CTL reconstitution was analyzed in the peripheral blood from 278 patients during the year following HSCT using 7 commercially available tetrameric HLA-CMV epitope complexes. All patients included could be monitored with at least CMV-specific tetramer., Results: CMV-CTL reconstitution was detected in 198 patients (71%) after allogeneic HSCT. Most importantly, reconstitution with 1 CMV-CTL per µl blood between day +50 and day +75 post-HSCT discriminated between patients with and without CMV reactivation in the R+/D+ patient group, independent of the CMV-epitope recognized. In addition, CMV-CTLs expanded more daramtaically in patients experiencing only one CMV-reactivation than those without or those with multiple CMV reactivations. Monitoring using at least 2 tetramers was possible in 63% (n = 176) of the patients. The combinations of particular HLA molecules influenced the numbers of CMV-CTLs detected. The highest CMV-CTL count obtained for an individual tetramer also changed over time in 11% of these patients (n = 19) resulting in higher levels of HLA-B*0801 (IE-1) recognizing CMV-CTLs in 14 patients., Conclusions: Our results indicate that 1 CMV-CTL per µl blood between day +50 to +75 marks the beginning of an immune response against CMV in the R+/D+ group. Detection of CMV-CTL expansion thereafter indicates successful resolution of the CMV reactivation. Thus, sequential monitoring of CMV-CTL reconstitution can be used to predict patients at risk for recurrent CMV reactivation.

Background Aims: Cytokine-induced killer (CIK) cells may serve as an alternative approach to adoptive donor lymphocyte infusions (DLI) for patients with acute leukemia relapsing after haplo-identical hematopoietic stem cell transplantation (HSCT). We investigated the feasibility of enhancing CIK cell-mediated cytotoxicity by interleukin (IL)-15 against acute myeloid and lymphoblastic leukemia/lymphoma cells., Methods: CIK cells were activated using IL-2 (CIK(IL-2)) or IL-15 (CIK(IL-15)) and phenotypically analyzed by fluorescence-activated cell sorting (FACS). Cytotoxic potential was measured by europium release assay., Results: CIK(IL-2) cells showed potent cytotoxicity against the T-lymphoma cell line H9, T-cell acute lymphoblastic leukemia (T-ALL) cell line MOLT-4 and subtype M4 acute myeloid leukemia (AML) cell line THP-1, but low cytotoxicity against the precursor B (pB)-cell ALL cell line Tanoue. IL-15 stimulation resulted in a significant enhancement of CIK cell-mediated cytotoxicity against acute lymphoblastic leukemia/lymphoma cell lines as well as against primary acute myeloid and defined lymphoblastic leukemia cells. However, the alloreactive potential of CIK(IL-15) cells remained low. Further analysis of CIK(IL-15) cells demonstrated that the NKG2D receptor is apparently involved in the recognition of target cells whereas killer-cell immunoglobulin-like receptor (KIR)-HLA mismatches contributed to a lesser extent to the CIK(IL-15) cell-mediated cytotoxicity. In this context, CD3 (+) CD8 (+) CD25 (+) CD56(-) CIK(IL-15) cell subpopulations were more effective in the lysis of AML cells, in contrast with CD56 (+) CIK(IL-15) cells, which showed the highest cytotoxic potential against ALL cells., Conclusions: This study provides the first evidence that CIK(IL-15) cells may offer a therapeutic option for patients with refractory or relapsed leukemia following haplo-identical HSCT.

Regulatory T cells (Tregs) are of crucial importance to suppress graft versus host disease (GvHD) post allogeneic stem cell transplantation (SCT), but are also known to impair antitumor immunity. However, Treg longitudinal studies are rare and in this respect advanced flowcytometric approaches for Treg characterization are necessary. To investigate the relation of both the percentage and the absolute numbers of Tregs on GvHD or relapse we measured CD4(+)CD25(+/hi)CD127(lo/-) Tregs in 239 peripheral blood (PB) samples of 16 patients during the first two years post-SCT. A 10-color flowcytometric panel was established to evaluate Treg subpopulations and has been tested in ten healthy individuals. In patients we demonstrated a decrease in CD127 expression on T cells early post-SCT which increases during the first year. Moreover, Tregs reached higher absolute numbers in patients with GvHD≤grade I compared to those with GvHD grades II-IV. In contrast, the percentage of Tregs was significantly higher in patients with GvHD grades II-IV or disease relapse compared to those without GvHD. These patients fit into the range of healthy individuals where a median value of 7.5% and 6.4% of T helper cells were characterized as CD4(+)CD25(+/hi)CD127(lo/-) and CD4(+)CD25(+/hi) Tregs, respectively. Furthermore, Tregs could be further subdivided into 40% naïve, 51% central memory and 9% effector memory Tregs. Our results showed for the first time a downregulation of CD127 expression on T cells including Tregs in patients early post-SCT. Additionally, new insights into the recovery of Tregs regarding GvHD and relapse were provided., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Allogeneic stem cell transplantation has become an important option in the curative treatment of many patients with malignant and non-malignant systemic diseases. Non-availability of HLA identical donors can limit access to this life-saving treatment, especially in ethnic minority patients, for whom identical donors are often not available [1,2]. For many years, a central aim has been the development of stem cell transplantation across the HLA barrier and the use of haploidentical parents as stem cell donors. Such an approach will allow allogeneic transplantation of all patients in need. During the past years, it has become possible to optimize in vitro graft manipulation procedures making this transplant procedure safer and more efficient. Therefore this haploidentical transplantation procedure can now serve as a basis for further cellular immunotherapy in the treatment of malignant and non-malignant diseases., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Severe acute graft versus host disease (GvHD) is a life-threatening complication after allogeneic hematopoietic stem cell transplantation. Human mesenchymal stromal cells (MSCs) play an important role in endogenous tissue repair and possess strong immune-modulatory properties making them a promising tool for the treatment of steroid-refractory GvHD. To date, a few reports exist on the use of MSCs in treatment of GvHD in children indicating that children tend to respond better than adults, albeit with heterogeneous results.We here present a review of the literature and the clinical course of two instructive pediatric patients with acute steroid-refractory GvHD after haploidentical stem cell transplantation, which exemplify the beneficial effects of third-party transplanted MSCs in treatment of acute steroid-refractory GvHD. Moreover, we provide a meta-analysis of clinical studies addressing the outcome of patients with steroid-refractory GvHD and treatment with MSCs in adults and in children (n = 183; 122 adults, 61 children). Our meta-analysis demonstrates that the overall response-rate is high (73.8%) and confirms, for the first time, that children indeed respond better to treatment of GvHD with MSCs than adults (complete response 57.4% vs. 45.1%, respectively).These data emphasize the significance of this therapeutic approach especially in children and indicate that future prospective studies are needed to assess the reasons for the observed differential response-rates in pediatric and adult patients.

Background: Reactivation of cytomegalovirus (CMV) is a major cause of morbidity after allogeneic hematopoietic stem cell transplantation (HSCT). In healthy individuals, virus-specific T cells (CMV-CTL) control the reactivation of latent CMV. The monitoring of virus-epitope-binding CD8(+) T cells using major histocompatibility complex-I-peptide complexes (tetramers) has recently been established, allowing assessment of the reconstitution of CMV-CTL post HSCT., Patients and Methods: In order to study immune reconstitution and reactivation control through CMV-CTL, we regularly monitored all patients undergoing allogeneic HSCT in our department for 2 years, who matched at least 1 of 6 commercially available tetramers for common human leukocyte antigen (HLA) types. To verify risk factors for CMV reactivations in our cohorts, clinical characteristics of all patients transplanted within the last 10 years were included in statistical analyses determining the relative risk for single and recurrent CMV reactivations., Results: As expected, CMV serostatus, HLA match, and donor source significantly influenced the risk of recurrent CMV reactivation. Applying CMV-CTL tetramer monitoring for 2 years allowed the monitoring of 114 (85%) of 134 patients, by testing a set of tetramers representing 6 epitopes from 3 different CMV proteins. The presence of CMV-CTL before day + 50 and their expansion post reactivation seem to protect against recurrent CMV reactivations. The mean number of CMV-CTL by day +100 was >5-fold higher in the recipient CMV-positive/donor-positive (R +/D +) group (91/μL) compared with the R +/ D- (13/μL) and the R -/D +(2/μL) group. Seventy-nine percent of patients from the R +/D + setting recovered >10 CMV-CTL per μL by day + 100, while almost 50% of the other groups failed to mount a CMV-specific response by that time (R +/D -: 58%; R -/D +: 43%)., Conclusion: Tetramer monitoring can help to predict (recurrent) CMV reactivation and is a useful approach to monitor individual patients with increased risk for recurrent reactivation post HSCT; thus, it could help to identify patients in need of adoptive transfer of CMV-CTL or to optimize the use of antiviral drugs., (© 2011 John Wiley & Sons A/S.)

The morbidity and mortality rates of invasive fungal infection in allogeneic stem cell recipients are still unacceptably high and have not been significantly improved by alternative antifungal strategies to date. Over the last few years, rapid methods for the clinical-scale generation of functionally active and well characterized antifungal T(H)1 cells have become available. In addition, current data on the use of donor-derived virus-specific T cells in allogeneic stem cell transplantation suggest that the risk of severe adverse events, in particular the risk of graft-versus-host disease, is negligible. Therefore, adoptive antifungal immunotherapeutic strategies should be evaluated in clinical trials. However, one has to recognize that these trials are only meaningful with sufficiently large and homogenous cohorts of patients and if the settings of adoptive antifungal immunotherapy are comparable. Ultimately, the strategy of adoptively transferring antifungal immune responses might improve the outcome in hematopoietic stem cell recipients suffering from invasive fungal infection.

Given that a significant proportion of children with acute lymphoblastic leukaemia (ALL) lose immune protection to tetanus, diphtheria, and poliomyelitis, revaccination is indicated after chemotherapy. Our randomized pilot study comparing different revaccination schedules suggests that children with ALL might be revaccinated with non-live vaccines as early as 3 months after chemotherapy., (© 2011 Blackwell Publishing Ltd.)

Human natural killer (NK) cells recognize and efficiently eliminate MHC class I low or negative malignant targets and virally infected host cells, without requirement for prior sensitization. However, viruses and various tumor cells display elaborate adaptations to evade and overcome immunosurveillance. The current review focuses on escape mechanisms of viruses and malignantly transformed 'stressed' cells to evade from NK cell cytotoxicity. A general overview of recent clinical studies using allogeneic donor NK cells is given, summarizing first data about a possible benefit for patients suffering from high-risk leukemia and solid tumors. Finally, the review discusses the future perspectives and hypotheses aiming to improve therapeutic NK cell strategies against tumor immune escape mechanisms., (Copyright © 2011 S. Karger AG, Basel.)

In an ongoing clinical phase I/II study, 16 pediatric patients suffering from high risk leukemia/tumors received highly purified donor natural killer (NK) cell immunotherapy (NK-DLI) at day (+3) +40 and +100 post haploidentical stem cell transplantation. However, literature about the influence of NK-DLI on recipient's immune system is scarce. Here we present concomitant results of a noninvasive in vivo monitoring approach of recipient's peripheral blood (PB) cells after transfer of either unstimulated (NK-DLI(unstim)) or IL-2 (1000 U/ml, 9-14 days) activated NK cells (NK-DLI(IL-2 stim)) along with their ex vivo secreted cytokine/chemokines. We performed phenotypical and functional characterizations of the NK-DLIs, detailed flow cytometric analyses of various PB cells and comprehensive cytokine/chemokine arrays before and after NK-DLI. Patients of both groups were comparable with regard to remission status, immune reconstitution, donor chimerism, KIR mismatching, stem cell and NK-DLI dose. Only after NK-DLI(IL-2 stim) was a rapid, almost complete loss of CD56(bright)CD16(dim/-) immune regulatory and CD56(dim)CD16(+) cytotoxic NK cells, monocytes, dendritic cells and eosinophils from PB circulation seen 10 min after infusion, while neutrophils significantly increased. The reduction of NK cells was due to both, a decrease in patients' own CD69(-) NCR(low)CD62L(+) NK cells as well as to a diminishing of the transferred cells from the NK-DLI(IL-2 stim) with the CD56(bright)CD16(+/-)CD69(+)NCR(high)CD62L(-) phenotype. All cell counts recovered within the next 24 h. Transfer of NK-DLI(IL-2 stim) translated into significantly increased levels of various cytokines/chemokines (i.e. IFN-γ, IL-6, MIP-1β) in patients' PB. Those remained stable for at least 1 h, presumably leading to endothelial activation, leukocyte adhesion and/or extravasation. In contrast, NK-DLI(unstim) did not cause any of the observed effects. In conclusion, we assume that the adoptive transfer of NK-DLI(IL-2 stim) under the influence of ex vivo and in vivo secreted cytokines/chemokines may promote NK cell trafficking and therefore might enhance efficacy of immunotherapy.

Despite the availability of new antifungal compounds, morbidity and mortality of invasive fungal disease in allogeneic hematopoietic stem cell recipients are still unacceptably high. Over the past decade, one could witness an exciting improvement of the understanding of the molecular pathogenesis and of the complexity of host antifungal immune responses. This, in turn, provides critical information to augment host immunity against fungal pathogens. Strategies for enhancing the immune system include the administration of effector and regulatory cells (e.g., granulocytes, antigen-specific T cells, dendritic cells) as well as the administration of recombinant cytokines, interferons and growth factors (e.g., interferon-γ, keratinocyte growth factor, granulocyte- and granulocyte-macrophage colony stimulating factor). One has to recognize at the same time, however, that data of in vitro assays and animal models cannot necessarily be transferred into the clinical setting. In addition, meaningful clinical trials in allogeneic stem cell recipients suffering from invasive fungal disease require sufficiently large and homogenous cohorts of patients and can only be performed in international collaboration, but may ultimately improve the outcome of allogeneic transplant recipients with invasive fungal disease.

We present a flexible and highly specific targeting method for lentiviral vectors based on single-chain antibodies recognizing cell-surface antigens. We generated lentiviral vectors specific for human CD105(+) endothelial cells, human CD133(+) hematopoietic progenitors and mouse GluA-expressing neurons. Lentiviral vectors specific for CD105 or for CD20 transduced their target cells as efficiently as VSV-G pseudotyped vectors but discriminated between endothelial cells and lymphocytes in mixed cultures. CD133-targeted vectors transduced CD133(+) cultured hematopoietic progenitor cells more efficiently than VSV-G pseudotyped vectors, resulting in stable long-term transduction. Lentiviral vectors targeted to the glutamate receptor subunits GluA2 and GluA4 exhibited more than 94% specificity for neurons in cerebellar cultures and when injected into the adult mouse brain. We observed neuron-specific gene modification upon transfer of the Cre recombinase gene into the hippocampus of reporter mice. This approach allowed targeted gene transfer to many cell types of interest with an unprecedented degree of specificity.

NK group 2D (NKG2D)-expressing NK cells exhibit cytolytic activity against various tumors after recognition of the cellular ligand MHC class I chain-related gene A (MICA). However, release of soluble MICA (sMICA) compromises NKG2D-dependent NK-cell cytotoxicity leading to tumor escape from immunosurveillance. Although some molecular details of the NKG2D-MICA interaction have been elucidated, its impact for donor NK (dNK) cell-based therapy of solid tumors has not been studied. Within an ongoing phase I/II trial, we used allogeneic IL-2 activated dNK cells after haploidentical stem cell transplantation for immunotherapy of patients with high-risk stage IV neuroblastoma. NKG2D levels on activated dNK cells increased strongly when compared with freshly isolated dNK cells and correlated with enhanced NK-cell cytotoxicity. Most importantly, elevated sMICA levels in patients plasma correlated significantly with impaired dNK-cell-mediated cytotoxicity. This effect could be reversed by high-dose infusion of activated dNK cells, which display high levels of surface NKG2D. Our data suggest that the provided excess of NKG2D leads to clearance of sMICA and preserves cytotoxicity of dNK cells via non-occupied NKG2D. In conclusion, our results identify this tumor immune escape mechanism as a target to improve immunotherapy of neuroblastoma and presumably other tumors., (Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Invasive fungal infections remain a serious and life-threatening complication in patients undergoing hematopoietic stem cell transplantation. Since it became clear that lymphocytes, in particular lymphocytes from the T helper 1 (T(H)1) subset, play a critical secondary defense against fungal pathogens, the adoptive transfer of functionally active antifungal T(H)1 cells might be an attractive option to restore adaptive antifungal immune effector mechanisms. Major advances have been made in the generation and characterization of antifungal T cells, which are active against medical important fungi such as Aspergillus spp and Candida spp. However, given the paucity of large homogenous patient populations, major challenges remain in evaluating the clinical usefulness of adoptive antifungal immunotherapy, which should be performed in international collaborative trials.

If insufficiently treated, Lyme borreliosis can evolve into an inflammatory disorder affecting skin, joints, and the CNS. Early innate immunity may determine host responses targeting infection. Thus, we sought to characterize the immediate cytokine storm associated with exposure of PBMC to moderate levels of live Borrelia burgdorferi. Since Th17 cytokines are connected to host defense against extracellular bacteria, we focused on interleukin (IL)-17 and IL-22. Here, we report that, despite induction of inflammatory cytokines including IL-23, IL-17 remained barely detectable in response to B. burgdorferi. In contrast, T cell-dependent expression of IL-22 became evident within 10 h of exposure to the spirochetes. This dichotomy was unrelated to interferon-γ but to a large part dependent on caspase-1 and IL-1 bioactivity derived from monocytes. In fact, IL-1β as a single stimulus induced IL-22 but not IL-17. Neutrophils display antibacterial activity against B. burgdorferi, particularly when opsonized by antibodies. Since neutrophilic inflammation, indicative of IL-17 bioactivity, is scarcely observed in Erythema migrans, a manifestation of skin inflammation after infection, protective and antibacterial properties of IL-22 may close this gap and serve essential functions in the initial phase of spirochete infection.

T-cell-based adoptive immunotherapy is widely used to treat graft rejection and relapse after stem cell transplantation (SCT). However, this approach is hampered by a high risk of life-threatening graft-versus-host-disease (GvHD). Clinical trials have demonstrated the value of suicide genes to modify T cells for the effective control of GvHD. Herewith, we show that the combination of a codon-optimized B-cell antigen (CD20op) with a selection marker based on a cytoplasmic truncated version of the human stem cell antigen CD34 (tCD34) allows the generation of highly enriched gene-modified T cells. We demonstrate coordinate co-expression of both transgenes and high expression of CD20op resulting in an increased susceptibility to Rituximab (RTX)-induced cell death. In addition, T cells partially retained their alloreactive potential and their CD4/CD8 ratio after transduction and expansion. Long-lasting transgene expression was sustained in vivo after adoptive transfer into Rag-1(-/-) mice. Moreover, gene-modified T cells were quickly and efficiently depleted from peripheral blood (PB) and secondary lymphoid organs of transplanted animals after RTX treatment. These results warrant further steps toward a clinical application of CD20op as a suicide gene for adoptive immunotherapy.

The speed of immune recovery after allo-SCT is of central importance to overcome infectious complications and relapse. To evaluate the immune reconstitution of pediatric patients concerning overall survival, we developed a three-component multivariate model and generated a reference domain of ellipsoidal shape on the basis of normal leukocyte subtype values of 100 healthy children and adolescents. The leukocyte subtypes include absolute nos. of leukocytes, CD14(+) monocytes, lymphocytes, CD3(+) T cells, CD3(+)CD4(+) helper T cells, CD3(+)CD8(+) cytotoxic T cells, CD3(-)CD56(+) natural killer-cells and CD19(+) B cells, all of which are correlated, thus, requiring the application of multivariate as opposed to multiple univariate modeling. According to their immune reconstitution, 32 pediatric patients post allo-SCT were classified into low-risk and high-risk groups on the basis of our new model. Therefore, we evaluated if the patients reached the ellipsoid of normal leukocyte sub-population values post SCT. We detected a significantly higher number of long-time survivors among the low-risk group compared with the high-risk group at days 200 (P=0.001) and 300 (P<0.0001). This is superior to our previously published univariate analysis. Combined with the clinical observation, a classification into risk groups based on an extended patient cohort may represent a predictor for complications.

Gene-modified autologous hematopoietic stem cells (HSC) can provide ample clinical benefits to subjects suffering from X-linked chronic granulomatous disease (X-CGD), a rare inherited immunodeficiency characterized by recurrent, often life-threatening bacterial and fungal infections. Here we report on the molecular and cellular events observed in two young adults with X-CGD treated by gene therapy in 2004. After the initial resolution of bacterial and fungal infections, both subjects showed silencing of transgene expression due to methylation of the viral promoter, and myelodysplasia with monosomy 7 as a result of insertional activation of ecotropic viral integration site 1 (EVI1). One subject died from overwhelming sepsis 27 months after gene therapy, whereas a second subject underwent an allogeneic HSC transplantation. Our data show that forced overexpression of EVI1 in human cells disrupts normal centrosome duplication, linking EVI1 activation to the development of genomic instability, monosomy 7 and clonal progression toward myelodysplasia.

To characterize natural killer (NK) cell subpopulations during activation, we analyzed the NK cell receptor repertoire and functionality of purified clinical scale CD56CD3 donor NK cells during stimulation with 1000 U/mL interleukin (IL)-2 for up to 14 days. In a phase I/II trial, we investigated the efficacy and feasibility of nonidentical NK cell infusion in patients with neuroblastoma after haploidentical stem cell transplantation. After IL-2 stimulation, large differences in the distribution of CD16 and CD16 subpopulations were found in 12 donors. Thereby, surface expression for all natural cytotoxicity receptors (NCRs) and NKG2D increased. In addition, killer cell immunoglobulin-like receptor (KIR) NK cells were overgrown by KIR proportion and the homing receptor CD62L was lost during stimulation. NK cell cytotoxicity against K562 and neuroblastoma cells increased and significantly higher cytokine secretion (eg, interferon-gamma, tumor necrosis factor-beta, macrophage inflammatory protein-1alpha, macrophage inflammatory protein-1beta) was observed after IL-2 stimulation compared with freshly isolated NK cells. However, NK cells of donors showing an initially enhanced cytotoxicity combined with NCR and CD69 expression, seemed to be exhausted and did not favor a stimulation period over 9 days. When IL-2-stimulated NK cells were given to transplant recipients, they induced a decrease of peripheral blood NK, in particular of CD56-NK cells. Our data indicate that IL-2 stimulation increases the expression of activating receptors and emphasizes mechanisms beside KIR/human leukocyte antigen. Furthermore, the results suggest that the expansion period of purified NK cells has to be individualized to optimize NK cell immunotherapy.

Recent studies have demonstrated that n-3 polyunsaturated fatty acids such as eicosapentaenoic acid (EPA) are able to suppress cell proliferation and inhibit tumor growth. The objective of our study was to investigate the influence of a high dose EPA on the development of the tumor phenotype in ataxia-telangiectasia mutated (Atm)-deficient mice, a genetic cancer model that is associated with increased levels of oxidative stress. We analyzed toxicity, proliferation, cell-cycle progression, and apoptosis of EPA in vitro and latency to tumorigenesis in vivo. Because of the impact of reactive oxygen species (ROS) on the tumor incidence in ataxia telangiectasia (AT), we further analyzed the effect of EPA on the generation of ROS and oxidative DNA damage (ODD). EPA effectively inhibited proliferation, altered cell-cycle progression, and induced apoptosis of tumor cells (AT-4). EPA showed no effect on the latency to tumorigenesis in Atm-deficient mice. EPA treatment was accompanied by a significant increase of ROS and ODD. Our results demonstrate the antiproliferative effect of EPA on tumor cells by alteration of cell-cycle progression and induction of apoptosis in vitro. On the other hand, EPA treatment of Atm-deficient mice led to the formation of ROS and accumulation of ODD that might have abrogated the anticarcinogenic effect caused by EPA.

Enrichment of cell subpopulations is a prerequisite for lineage-specific chimerism analysis (LCA), a frequent approach in follow-up after allo-SCT. An efficient enrichment technique is Magnetic Cell Sorting (MACS) using the AutoMACS separator. However, evaluation of purity, recovery and applicability for PCR-based chimerism analysis of MACS-enriched subpopulations from post-transplant peripheral blood, providing reduced cell numbers and/or unbalanced proportions of subpopulations, is currently unavailable. We performed enrichment of CD3-, CD14-, CD15-, CD19- and CD56-positive subpopulations using 'Whole Blood MicroBeads' and AutoMACS separator in 137 prospectively collected peripheral blood samples from 15 paediatric patients after allo-CD3-/CD19-depleted SCT. Purity was assessed by immune phenotyping. Recovery and applicability for chimerism analysis was evaluated. Excellent purity >90% was achieved in CD14-, CD15-positive cells in 81%, 95% of the isolates and in 86% of CD3 and CD19 isolates, if ACC was >400 cells per mul. Median purity of CD56-positive isolates was 78.9%. Recovery >90% was between 93 (CD56) and 37% (CD15). Conventional and real-time PCR-based chimerism analysis was feasible in virtually all samples. Isolation of cell subpopulations by automated cell enrichment in post-transplant peripheral blood is feasible and fast providing excellent purity and recovery for routine lineage-specific chimerism analysis.

Although the substantial risk for invasive pneumococcal disease is well recognized in children after allogeneic stem cell transplantation, little is known about the specific immunity against pneumococci in children after cytotoxic therapy for acute lymphoblastic leukaemia (ALL). We therefore assessed the spontaneous reconstitution of humoral immunity against pneumococcal antigens, of total IgG and the IgG2 subclass, and of lymphocyte subsets in a total of 53 children treated for ALL. None of the patients had received pneumococcal vaccination prior to or after therapy for ALL. At 3 and 9 months after completion of chemotherapy, most patients had levels of specific antibodies to pneumococcal antigens below the presumed threshold of protection and significantly lower than those of age-matched unvaccinated healthy controls. In contrast, at 9 months after completion of therapy, only a minority of patients had immunoglobulin concentrations or lymphocyte subset counts below the age-matched reference value. Our data indicate that patients with ALL who are unvaccinated against pneumococci have a selective immunodeficiency with an impaired antibody protection against pneumococci for up to 9 months after completion of therapy. Therefore, effective prevention, including chemoprophylaxis and active immunization, has to be considered in this patient population.

Chromosomal rearrangements of the human MLL gene are associated with high-risk pediatric, adult and therapy-associated acute leukemias. These patients need to be identified, treated appropriately and minimal residual disease was monitored by quantitative PCR techniques. Genomic DNA was isolated from individual acute leukemia patients to identify and characterize chromosomal rearrangements involving the human MLL gene. A total of 760 MLL-rearranged biopsy samples obtained from 384 pediatric and 376 adult leukemia patients were characterized at the molecular level. The distribution of MLL breakpoints for clinical subtypes (acute lymphoblastic leukemia, acute myeloid leukemia, pediatric and adult) and fused translocation partner genes (TPGs) will be presented, including novel MLL fusion genes. Combined data of our study and recently published data revealed 104 different MLL rearrangements of which 64 TPGs are now characterized on the molecular level. Nine TPGs seem to be predominantly involved in genetic recombinations of MLL: AFF1/AF4, MLLT3/AF9, MLLT1/ENL, MLLT10/AF10, MLLT4/AF6, ELL, EPS15/AF1P, MLLT6/AF17 and SEPT6, respectively. Moreover, we describe for the first time the genetic network of reciprocal MLL gene fusions deriving from complex rearrangements.

A monoclonal chimeric antibody ch.MK1 was generated by immunizing F004 mice expressing human instead of murine IgG1/kappa immunoglobulin constant regions. The novel antibody specifically binds cell surface-expressed human neural cell adhesion molecule (NCAM) as shown by immunoprecipitation, flow cytometry and cytospins. Functional analysis revealed nearly complete absence of complement-dependent cytolysis in ch.MK1 and in all other anti-NCAM antibodies tested for reference (UJ13a, ERIC1, 123C3, ch.5A2, B159), indicating an unexpected and group-specific property of anti-NCAM antibodies. As a most plausible mechanism, posttranslational modification of NCAM by complement-inhibiting polysialic acid is discussed. The antibody ch.MK1 demonstrated significant in vivo activity against NCAM-positive neuroblastoma in SCID mice in presence of human peripheral blood mononuclear cell. In absence of human peripheral blood mononuclear cell no distinct antitumor activity of the antibody alone was observed. In ch.MK1 the cellular component of the immune system seems to be the dominant effector mechanism, whereas complement-dependent cytolysis seems not to be necessarily required for antitumor activity. These observations help us to understand immunotherapeutic mechanisms of native anti-NCAM antibodies and may additionally contribute to the understanding of results of currently ongoing clinical studies with conjugated anti-NCAM antibodies.

Background: Because of a high risk of graft-versus-host disease (GVHD), donor lymphocyte infusions with unmodified lymphapheresis products are not used after haploidentical hematopoietic stem cell transplantation. Natural killer (NK) cells have antitumor activity and may consolidate engraftment without inducing GVHD. Production of NK cells under good manufacturing practice (GMP) conditions in a sufficient number is difficult., Study Design and Methods: Twenty-four apheresis procedures and subsequent NK-cell enrichment from 14 haploidentical donors were performed. NK-cell enrichment was performed using a GMP suitable immunomagnetic procedure. Factors influencing the NK-cell recovery, purity, and NK-cell dose were analyzed., Results: A median number of 4.9 x 10(8) NK cells were obtained and median NK-cell recovery was 58 percent. Median T-cell depletion was 4.32 log. The absolute NK-cell number in the final product after processing significantly correlated with the preharvest NK-cell content of the peripheral blood (p = 0.002, r = 0.867). The NK-cell recovery was inversely correlated to the absolute NK-cell number in the apheresis product (p = 0.01, r = -0.51). The NK-cell dose per kg of body weight of the patient was inversely correlated to the weight of the patient (p = 0.007, r = -0.533)., Conclusion: Donors with a high NK-cell count in peripheral blood are likely to provide NK-cell products with the highest cell number. However, maximal NK-cell dose is limited and high NK-cell doses may only be obtained for patients with a low body weight, making children and young adults the best candidates for NK-cell therapy.

Invasive aspergillosis remains a serious complication in patients undergoing allogeneic stem cell transplantation. Since it became clear that lymphocytes provide a critical secondary defense against fungi, adoptive transfer of functionally active anti-Aspergillus T cells might be an option to restore adaptive immune effector mechanisms. Using the interferon (IFN)-gamma secretion assay, we isolated human activated T cells upon stimulation with a cellular extract of Aspergillus fumigatus. After a culturing period for 14 days, we could characterize these cells as T(H)1 cells, which also proliferated upon restimulation. The generated cells responded upon stimulation with antigens of A. flavus, A. niger and Penicillium chrysogenum, but not upon activation with Alternaria alternata and Candida albicans. In addition, the cultivated T cells were able to induce damage to A. fumigatus hyphae and showed a reduced alloreactivity compared to unselected CD4+ T cells. We further established a clinical-scale generation of anti-Aspergillus T cells. However, before performing clinical trials, open questions such as which patient population will benefit from adoptive immunotherapy with anti-Aspergillus T cells have to be addressed.

Invasive aspergillosis is a major cause of morbidity and mortality in patients undergoing allogeneic hematopoietic SCT. There is a growing body of evidence that T cells are important in the host defense against Aspergillus, and adoptively transferred anti-Aspergillus T-helper 1 (T(H)) 1 cells might reduce infectious mortality in hematopoietic transplant recipients. Here we present for the first time a simple and rapid method for the clinical-scale generation of functionally active anti-Aspergillus T cells according to good manufacturing practice conditions. A total of 1.1 x 10(9) WBCs derived from a leukapheresis product were incubated with Aspergillus antigens. Stimulated cells were selected by means of the IFN-gamma secretion assay and expanded. In three independent experiments, a median number of 2 x 10(7) CD3+CD4+cells (range, 0.9-3.2 x 10(7)) were obtained within 13 days. The cultured CD3+CD4+ cells exhibited almost exclusively a memory activated T-helper cell phenotype. Upon restimulation, the generated T cells produced IFN-gamma, but no IL-4 or IL-10, indicating a T(H)1-cell population. Additionally, the cells proliferated upon restimulation and showed reduced alloreactivity compared to unselected CD4+ cells. This method of generating is suitable for future prospective trials designed to evaluate the effect of adoptive immunotherapy in hematopoietic transplant recipients with invasive aspergillosis.

Purpose: The alkylating agent treosulfan exerts a high cytotoxic activity against various malignant cells. Due to limited non-hematological toxicity, treosulfan might be a promising compound in myeloablative therapy for hematopoietic transplantation in children. Since in vitro data regarding the activity of treosulfan against childhood leukemic cells are limited, we compared the effect of treosulfan and busulfan against pediatric leukemic and non-malignant cells., Experimental Design: Both agents were tested alone and in combination with fludarabine by means of the MTT and/or a five color-flow cytometric assay. Moreover, the induction of apoptosis by treosulfan was investigated via regulation of the proteinase caspase 3., Results: Treosulfan was more active against leukemic cells of 20 children as well as against 3 leukemia-derived cell lines than busulfan, with increasing IC50 values from initial diagnosis to relapse. Overall purified stem cells were most sensitive, followed by CD56+CD3- NK and CD3+ T cells. The combination of treosulfan with fludarabine resulted in a synergistic effect against leukemic cells. In malignant cells, treosulfan induced rapid cell apoptosis measured by the activation of the centrally proteinase caspase 3., Conclusion: Our results indicate that treosulfan has activity against pediatric leukemic cells, myeloablative potential and immunosuppressive properties suitable for conditioning regimen in childhood malignancies.

Retargeting of lentiviral vector entry to cell types of interest is a key factor in improving the safety and efficacy of gene transfer. In this study we show that the retargetable envelope glycoproteins of measles virus (MV), namely, the hemagglutinin (H) responsible for receptor recognition and the fusion protein (F), can pseudotype human immunodeficiency virus 1 (HIV-1) vectors when their cytoplasmic tails are truncated. We then pseudotyped HIV-1 vectors with MV glycoproteins displaying on H either the epidermal growth factor or a single-chain antibody directed against CD20, but without the ability to recognize their native receptors. Gene transfer into cells that expressed the targeted receptor was several orders of magnitude more efficient than into cells that did not. High-target versus nontarget cell discrimination was demonstrated in mixed cell populations, where the targeting vector selectively eliminated CD20-positive cells after suicide gene transfer. Remarkably, primary human CD20-positive B lymphocytes were transduced more efficiently by the CD20-targeted vector than by a vector pseudotyped with the vesicular stomatitis virus G (VSV-G) protein. In addition, the CD20-targeted vector was able to transduce even unstimulated primary B cells, whereas VSV-G pseudotyped vectors were unable to do so. Because MV enters cells through direct fusion at the cell membrane, this novel targeting system should be widely applicable.